Methods and Circuits for Controlling a Battery Disconnect Switch

ABSTRACT

Redundant power supplies and redundant channels of communication maximize the probability that a controller will trigger a battery disconnect switch to open when commanded to do so.

FIELD OF THE INVENTION

This invention relates generally to electrical systems of motorvehicles. More particularly, the invention relates to circuits thatinclude a battery disconnect switch for disconnecting a battery orbattery bank from the electrical system.

BACKGROUND OF THE INVENTION

Motor vehicles that are propelled by internal combustion engines haveelectrical systems that include one or more D.C. storage batteries. Inorder to crank the engine at starting, an ignition switch is turned to astart, or crank, position that causes the engine to be cranked by anelectric starter motor. When the engine has started, the switch isreleased from start position to assume a run position. In startposition, electric current flows from the battery, or battery bank, toan electric starter motor that cranks the engine through a set of gears.The amount of current is typically very large, and consequently, heavyelectrical cable is typically employed to conduct the current withoutthe presence of any circuit protection device to protect against a shortin the cable or the starter motor.

The electrical system has other circuits that are fed from the battery,or battery bank. Those individual circuits may be protected by their ownindividual circuit protection devices, such as fuses or circuitbreakers, but there may be no circuit protection between the battery andthe circuit protection devices themselves unless a battery disconnectswitch is present.

Various types of battery disconnect switches are known. One type is amechanical switch that requires manual operation. Because it may not befeasible to access such a switch in a hazardous situation, such as aftera vehicle has been involved in an accident, automatic remote controlsystems for operating battery disconnect switches have been developed.

When a vehicle is equipped with a passenger airbag system, a signal thatcalls for airbag deployment may also be used to remotely operate abattery disconnect switch. A medium or heavy truck that may have abattery disconnect switch, typically does not have an airbag system, andso the same type of control remote control that would be present in anairbag equipped vehicle would not be present in the truck.

SUMMARY OF THE INVENTION

The inventors have recognized that failure to open a battery disconnectswitch that connects the battery bank with a vehicle's electrical systemmay in certain situations have serious negative consequences. Theinventors therefore believe that it is important to minimize, andideally reduce to zero, the probability that the switch will fail toopen when commanded to do so. Failure of the switch to open may be dueto no fault in the design or quality of the switch itself or thevehicle's electrical system, but rather may be due to circumstances of aparticular situation, such as a crash.

The inventors therefore propose that the system for operating thebattery disconnect switch employ certain features that will maximize theprobability that a battery disconnect switch will open when commanded todo, even if the vehicle is not equipped with an airbag system that isintended to open the disconnect switch in the event of a crash.

These features include redundant channels of communication through whicha command to open the switch is transmitted from one or more sources ofthe command to a controller, and redundant power supplies for the switchand the controller.

It is a general objective of the invention to provide an electricalsystem connected through a battery disconnect switch to a bank of one ormore DC storage batteries. A battery disconnect switch controller willopen the battery disconnect switch in response to a command todisconnect the battery bank from the electrical system. The system hasredundant channels of communication through which the command istransmitted from one or more sources of the command to the controller.

It is another general objective of the invention to provide anelectrical system connected through a battery disconnect switch to abank of one or more DC storage batteries. A battery disconnect switchcontroller will open the battery disconnect switch in response to acommand to disconnect the battery bank from the electrical system. Thesystem has redundant power supplies for the switch and the controller.

The foregoing, along with further aspects, features, and advantages ofthe invention, will be seen in the following disclosure of a presentlypreferred embodiment of the invention depicting the best modecontemplated at this time for carrying out the invention. The disclosureincludes drawings, briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general schematic electrical diagram of a first circuitembodying principles of the present invention.

FIG. 2 is a general schematic electrical diagram of a second circuit.

FIG. 3A is a schematic electrical diagram of a first type of batterydisconnect switch that can be controlled in accordance with principlesof the invention.

FIG. 3B is a schematic electrical diagram of a second type of batterydisconnect switch that can be controlled in accordance with principlesof the invention.

FIG. 3C is a schematic electrical diagram of a third type of batterydisconnect switch that can be controlled in accordance with principlesof the invention.

FIG. 4 is more detailed schematic diagram of a version of the circuit ofFIG. 1 that is used with disconnect switch trigger circuits shown inFIGS. 5A and 5C.

FIG. 5A is a schematic electrical diagram of a trigger circuit for usein triggering the first type of battery disconnect switch.

FIG. 5B is a schematic electrical diagram of a trigger circuit for usein triggering the second type of battery disconnect switch.

FIG. 5C is a schematic electrical diagram of a trigger circuit for usein triggering the third type of battery disconnect switch.

FIG. 6 is a more detailed schematic diagram of a version of the circuitof FIG. 1 that is used with the disconnect switch trigger circuit shownin FIG. 5B.

FIGS. 7 and 8 collectively form a schematic diagram of the power supplyand voltage regulator used in the circuits of FIGS. 1 and 6.

FIG. 9 is a more detailed schematic diagram of the second circuit shownin FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a circuit that comprises one or more D.C. storage batteries20, herein sometimes referred to as a battery bank, a battery disconnectswitch 22, herein sometimes referred to as a BDS, a starter motor 24 forcranking an internal combustion engine that propels a truck, and acontrol unit 26 for operating BDS 22. Ignition switch connection tostarter motor 24 is not shown. Control unit 26 and BDS 22 are integratedwith battery bank 20 on the truck chassis.

BDS 22 assumes a normally closed condition for conducting current frombattery bank 20 to starter motor 24 when the ignition switch is placedin start position to crank the vehicle's engine. When control unit 26receives a signal requesting that BDS 22 be operated to open condition,the control unit delivers a trigger signal to BDS 22 that causes BDS 22to open and prevent current flow from battery bank 20 to starter motor24.

Control unit 26 can receive signals from an HMI (human machineinterface) 28, a wired communication channel 30, and a wirelesscommunication channel 32. Wired and wireless communication are redundantin the disclosed embodiment, meaning that a signal request to operateBDS 22 to open is concurrently sent by both wire and wireless channelsfrom a location that is remote from the battery bank. HMI 28 isunderstood to be an operator, such as a pushbutton, at the location ofthe switch.

FIG. 2 shows a second control unit 34 that receives signals from HMI 28and re-transmits them to control unit 26 both by wire and wireless.Control unit 34 is remote from control unit 26 and is located, forexample, in the instrumental panel of the truck cab.

FIGS. 3A and 3B illustrate respective relay type BDS actuators. FIG. 3Cillustrates a pyroelectric type BDS actuator. These three actuators arepresent in known battery disconnect switches.

In FIG. 3A, the receipt of a trigger signal T by actuator 36 causes theactuator to open BDS 22. When no trigger signal is given, BDS 22 isclosed.

When a voltage whose polarity is represented by numeral 40 in FIG. 3B isapplied to actuator 38, BDS 22 is closed. When a voltage of oppositepolarity, as represented by numeral 42, is applied, BDS 22 is open.

When a voltage is applied to actuator 44 in FIG. 3C, BDS 22 isirreversibly opened.

FIG. 4 shows control unit 26 to comprise a power supply and voltageregulator 50 powered by battery bank 20 for developing a regulatedvoltage 52, such as +12 VDC, that is supplied to BDS 22 and a regulatedvoltage, such as +5 VDC, for operating a microcontroller system (MCS)54. A back-up power supply 56 is provided for power supply and voltageregulator 50 in case the latter's connection to the battery bank throughthe vehicle electrical system is somehow lost.

MCS 54 will trigger BDS 22 via a trigger circuit 58 when MCS 54 receivesa command to disconnect battery bank 20 from the vehicle electricalsystem. The command may come from any one or more of three sources,namely from the non-remote HMI input directly to MCS 54, from a remoteinitiator via wired communication, and from a remote initiator viawireless communication. Wired communication to MCS 54 is through one ormore of an SAE J1939 and an SAE J1708 data link. Wireless communicationcan occur via one or more wireless communication protocols such asZigbee and Bluetooth.

FIG. 5A shows how MCS 54 is associated with the actuator 36 of FIG. 3A.The trigger circuit 58 comprises a transistor driver in which thecollector is connected to one terminal of actuator 36. The otherterminal of actuator 36 is connected to battery bank 20 through BDS 22.When MCS 54 operates the transistor driver, actuator 36 becomes groundedthrough the transistor. Battery current flows through BDS 22, actuator36 and the transistor to ground causing the actuator to open BDS 22 andautomatically terminating the current flow to ground through actuator36.

FIG. 5B shows how MCS 54 is associated with the actuator of FIG. 3B.Voltage is applied to actuator 38 in the polarity sense of referencenumeral 40 when a first transistor driver 40A is turned on by MCS 54.Voltage is applied to actuator 38 in the polarity sense of referencenumeral 42 when a second transistor driver 42A is turned on by MCS 54.Both battery voltage (20) and regulated voltage (52) are supplied to thecollector of driver 40A through respective diodes D1, D2. Both batteryvoltage (20) and regulated voltage (52) are also supplied to thecollector of driver 42A through respective diodes D3, D4. Diodes D5, D6provide reverse polarity protection for the respective driver drivers.

FIG. 5C shows how MCS 54 is associated with the actuator of FIG. 3C. Thetrigger circuit 58 comprises a transistor driver in which the collectoris connected to one terminal of actuator 44. The other terminal ofactuator 44 is connected to battery bank voltage (20) and to regulatedvoltage (52) through respective diodes D1, D2.

FIG. 6 shows control unit 26 to comprise a microcontroller system (MCS)70 that is associated with the wired communication channel, the wirelesscommunication channel, and the HMI interface.

MCS 70, like MCS 54, monitors battery bank voltage as an indicator ofthe healthy status of the battery bank and the associated battery cablesystem. Should the battery bank voltage become less than voltage neededto operate the BDS actuator, microcontroller 70 outputs regulated +12Vto the trigger circuit (reference 52) to provide enough power supply forthe BDS to function correctly when the microcontroller is commanded todisconnect the battery bank via the trigger circuits.

Microcontroller 70 can receive a command input from the HMI interface,from the wired communication interface, or the wireless communicationinterface. A J1939 communication is used as a standard wiredcommunication interface. A J1708 is optionally available for a vehiclethat has no J1939 network.

For redundancy, Zigbee wireless communication technology is implemented.Bluetooth wireless communication technology is used as an option forcontrol interface expansibility. The redundancy of wired communicationand wireless communications increases the probability that BDS will beshut off when commanded.

FIG. 7 illustrates details of the power supply and voltage regulator 50.A step up/step down DC/DC converter 90 with burst mode can developregulated +12 VDC output from input voltages ranging from +4 VDC to +60VDC. One input to converter 90 is from the battery bank through a diode.Another input is from the back-up power circuit 56. A voltage regulator92 develops +5 VDC for the microcontroller system from the output ofconverter 90.

FIG. 8 illustrates back-up power circuit 56. It comprises asuper-capacitor 100 and a back-up battery pack 102. The super-capacitor100 is charged from the battery bank through a diode D7. Battery pack102 parallels super-capacitor 100 and is kept charged from the batterybank.

FIG. 9 shows control unit 34. A microcontroller 104 can read a usercommand from a push button with energy harvest module 106 and transmitthe command to control unit 26 through wired and/or wireless channels.When the push button is pushed, the energy harvest module provides powerto assure the microcontroller and Zigbee module both perform the userrequest. This enables control unit 34 to still send a command to controlunit 26 should the power supply to the MHI interface and/or wiredcommunication channel become non-functional, such as in an accident.

While a presently preferred embodiment of the invention has beenillustrated and described, it should be appreciated that principles ofthe invention are applicable to all embodiments that fall within thescope of the following claims.

1.-10. (canceled)
 11. A motor vehicle comprising: an electrical systemconnected through a battery disconnect switch to a bank of one or moreDC storage batteries; a battery disconnect switch controller for openingthe battery disconnect switch in response to a command to disconnect thebattery bank from the electrical system; redundant power supplies forthe switch and the controller.
 12. A motor vehicle as set forth in claim11 wherein the redundant power supplies comprise the battery bank and apower supply and regulator for supplying regulated voltages of differentlevels, one voltage level being supplied to a microcontroller thatprocesses a command to open the disconnect switch and another voltagelevel being supplied to the disconnect switch.
 13. A motor vehicle asset forth in claim 11 wherein the power supply and regulator comprises aDC-to-DC converter that outputs the voltage level supplied to thedisconnect switch and including a further regulator that has an inputreceiving the voltage level output of the DC-to-DC converter and anoutput that provides the voltage level supplied to the microcontroller.14. A motor vehicle as set forth in claim 13 wherein the DC-to-DCconverter comprises an input that is coupled via a diode with thebattery bank and also coupled via another diode with a back-up source ofDC voltage that is kept sufficiently charged by a connection to thebattery bank to provide enough electrical power to the controller toenable the controller to operate the disconnect switch if battery bankpower is lost to the controller.